The words herd and heard sound similar when spoken, but are different words.
The word herd can be used both as a noun and as a verb.
(a) The word herd as a noun has the following meanings: group; flock; pack. It can thus refer to people or animals as the case may be.
(b) The word herd as a verb means: shepherd; usher; guide; direct; steer; channel.
The word heard refers to the past tense of the word hear (which means to listen to, heed, pay attention to or simply to perceive sound).
(a) Examples of Herd as a Noun:
1. The rancher found it difficult to herd his cattle quickly before the rain began.
2. A herd of cows broke the fencing and strayed on to the road.
3. It is important to decide on one's own career and not simply follow the herd.
(b) Examples of Herd as a Verb:
1. The teacher herded the children towards the playground.
2. When the fire alarm went off, the restaurant manager quickly herded the diners towards safety.
3. The crowd was herded willy-nilly by the police to keep them away from the dignitaries.
Examples of Heard:
1. The music composer was impressed by the young lad's talent when he heard his songs in the reality show.
2. I heard a sudden noise behind me and turned around in alarm.
3. We heard loud noises from the party at the neighbour's house and hence could not hear the television commentary clearly.